This invention relates to mounting semiconductor die on a support.
A semiconductor integrated circuit die may be mounted directly onto a printed circuit board; or on a leadframe or a substrate; or on another semiconductor die in a stacked die assembly.
A semiconductor integrated circuit die is conventionally mounted on the support using an adhesive. Die mount adhesives may take the form of a die attach epoxy, as illustrated for example in FIGS. 1 and 2; or an adhesive film, as illustrated for example in FIGS. 3 and 4.
FIG. 1 shows an assembly including a die 22 mounted on a substrate 10 using a die attach epoxy. The die 22 has a front side (“active” side) 23 adjacent which the integrated circuitry is formed, and a back side 21, and sidewalls meeting the front and back sides at front and back edges. Die pads at the front side of the die, arranged in this example as peripheral pads 24, provide for electrical connection of the integrated circuitry of the die with underlying circuitry.
The substrate 10 in this example includes a patterned metal layer 12 on a dielectric layer. The patterned metal layer 12 is covered by an electrically insulative layer 13, which has openings exposing bond fingers 11. The substrate may include one or more additional patterned metal layers, variously connected at vias through intervening dielectric layers, including a patterned metal layer at the surface opposite the die mount surface, at which lands are exposed to provide for connection to circuitry in a device in which the assembly is deployed.
The die 22 is in this example affixed to a die mount region of the substrate by a die attach epoxy 32. The die mount procedure includes dispensing a specified quantity of epoxy onto the insulative layer 13, placing the die onto the epoxy, and curing the epoxy. Typically a “fillet” 33 is formed outside the die footprint at the periphery of the die mount region. The epoxy die attach process is carefully controlled to provide for a uniform die attach epoxy thickness and a limited spread of epoxy onto the substrate outside the die footprint. Following die attach, the die is electrically connected to the circuitry on the substrate by wire bonds 14 connecting pads 24 with bond fingers 11. A molding or encapsulation (not shown in the FIG.) may be formed over the assembly to protect the active side of the die and the interconnects.
FIG. 2 shows an assembly including a first die 22 mounted on a substrate 10 generally as described with reference to FIG. 1, and including an additional die 26 mounted on the first die 22 using a die attach epoxy. The additional die 26 has a front side (“active” side) 27 adjacent which the integrated circuitry is formed, and a back side 25, and sidewalls meeting the front and back sides at front and back edges. Die pads at the front side of the die, arranged in this example as peripheral pads 28, provide for electrical connection of the integrated circuitry of the die with underlying circuitry.
The second die 26 is in this example affixed to a die mount region on the front side 23 of the first die 22 by a die attach epoxy 34. The second die mount procedure, as with the first die mount procedure, includes dispensing a specified quantity of epoxy onto a die attach region of the front side of die 22, placing the second die onto the epoxy, and curing the epoxy. Typically a “fillet” 35 is formed outside the die footprint at the periphery of the die mount region. As in the first die attach process, this second epoxy die attach process is carefully controlled to provide for a uniform die attach epoxy thickness and a limited spread of epoxy onto the first die surface 23 outside the die footprint. Following die attach, the die is electrically connected to the circuitry on the substrate by wire bonds 16 connecting pads 28 with bond fingers 11. A molding or encapsulation (not shown in the FIG.) may be formed over the assembly to protect the active side of the die and the interconnects.
FIG. 3 shows an assembly including a die 22 mounted on a substrate 10 using a film adhesive 42. The die and the substrate, and their electrical connections to the substrate, are as in the example shown in FIG. 1.
The die 22 is in this example affixed to a die mount region of the substrate by a film adhesive 42. The die mount procedure includes applying the film to either the backside of the die 22 or to the die mount region of the substrate 10, thereafter placing the die onto the insulative layer 13 on the substrate, and thereafter (where the adhesive is curable) curing the adhesive. Where the adhesive film is applied to the substrate, the film must first be cut to size, and then positioned on the substrate surface; where the film is applied to the die, this step may be performed at the wafer level, so that the film is cut to size during die singulation. Following die attach, the die is electrically connected to the circuitry on the substrate by wire bonds 14 connecting pads 24 with bond fingers 11. A molding or encapsulation (not shown in the FIG.) may be formed over the assembly to protect the active side of the die and the interconnects.
FIG. 4 shows an assembly including a first die 22 mounted on a substrate 10 generally as described with reference to FIG. 3, and including an additional die 26 mounted on the first die 22. The die and the substrate, and their electrical connections to the substrate, are as in the example shown in FIG. 3. The second die mount procedure, as with the first die mount procedure, includes applying the film to either the backside of the die 26 or to the die mount region of the front side of the first die 22, thereafter placing the second die onto the first die, and thereafter (where the adhesive is curable) curing the adhesive. Where the adhesive film is applied to the substrate, the film must first be cut to size, and then positioned on the surface of the first die; where the film is applied to the second die, this step may be performed at the wafer level, so that the film is cut to size during second die singulation. Following die attach, the second die is electrically connected to the circuitry on the substrate by wire bonds 16 connecting pads 28 with bond fingers 11. A molding or encapsulation (not shown in the FIG.) may be formed over the assembly to protect the active side of the die and the interconnects.